High tensile strength elastomeric adhesive cements and laminates therefrom

ABSTRACT

Adhesive contact cements of sulfonated olefinically unsaturated elastomers (sulfobutyl rubber) containing from about 0.1 to about 5.0 mol % SO 3  H neutralized, partially neutralized, or unneutralized, are admixed with tackifiers, i.e. phenolformaldehyde resins, polyisobutylene, alkylphenol formaldehyde resins, petroleum resins, etc. in an amount of between about 5 and about 90 phr in between about 10 and about 50 wt. % solids concentration in organic solvents. These cements are used for adhering porous or non-porous materials such as textiles, wood, cloth, sheets or strip of metals, plastics, etc. to each other. High green strength, high tensile strength, high resistance to peel, even at elevated temperatures, water impermeability, etc. characterize such adhesive layers in laminates. A preferred solvent, 90% toluene, 10% isopropyl alcohol is used in compounding the cement and preferably an organic amine, e.g. ethylamine, is used to partially or completely neutralize the sulfonated elastomer although inorganic bases may also be used for neutralization.

This is a division of application Ser. No. 209,414, filed Dec. 17, 1971,now U.S. Pat. No. 3,867,247, issued Feb. 18, 1975.

DESCRIPTION OF THE INVENTION

This invention relates to high tensile strength elastomeric adhesivecements and to laminated substrates employing such cements as theadhesive layer holding the substrates to each other in laminated form.Elastomers such as natural rubber or synthetic elastomers such as butylrubber, halobutyl rubber, or other olefinically unsaturated elastomerssuch as SBR, polyisoprene, polybutadiene, polychloroprene,ethylene-diene propylene terpolymers, are curable by cross linking orotherwise being vulcanized. The most general method of vulcanization ofsuch materials involves the use of sulfur and sulfur compounds. However,chemical (peroxide) vulcanization is also utilized in many instances.

Sulfonic acid polymers and copolymers of such elastomers have beenprepared in the past by well known methods, for example, aromaticcontaining polymers are sulfonated as described in U.S. Pat. No.3,072,618 using a complex of a lower alkyl phosphate and sulfurtrioxide. Water soluble polymers have been prepared by reacting thearomatic rings in styrene-butyl rubber graft polymers with SO₃ to formviscous sulfonated products as described in Soviet Pat. No. 211,079. Theolefinically unsaturated elastomers, including natural rubber as well asthe synthetic elastomers, have been sulfonated using chlorosulfonic acidwith ethers and esters as described in German Pats. Nos. 582,565,550,243 and 572,980. U.S. Pat. No. 3,205,285 teaches that the ability totake up dyes in the case of polypropylene fibers is enhanced by reactingthe fibers with an SO₃ complex.

More recently sulfonated elastomers have been prepared of particularsulfo-group content by the reaction of the natural or syntheticelastomers using various complexes of SO₃. This is described, in detail,in pending U.S. Patent Application 877,849, filed Nov. 18, 1969, whichhas issued as U.S. Pat. No. 3,642,728 issued Feb. 15, 1972. Thisdisclosure is incorporated herein by reference since the sulfonatedproducts produced as described in that patent are one type of usefulsulfonated elastomers forming the chief component of the contact cementshereinafter described. Additionally, another method of producing thesulfonated elastomers again of limited mole % sulfo group content andhaving unique properties are prepared by the reaction of theolefinically unsaturated rubbers with acyl sulfate. These sulfonatedelastomers differ to some extent chemically from those described in thelast mentioned U.S. patent, but in general both types of sulfonatingtechniques have been used to prepare sulfonated butyl rubbers whichexhibit high green strengths, high tensile strengths, which have a highwater impermeability and which possess other advantageous properties notheretofore present in previously produced sulfonated elastomers. Themethod of preparation of these sulfonated elastomers using acyl sulfatesis described in pending U.S. Application Ser. No. 123,908, filed Mar.12, 1971 by O'Farrell and Serniuk and now abandoned, which disclosure isincorporated hereinto by reference.

The rubbers which may be sulfonated are the olefinic and unsaturatedelastomers such as butyl rubber, halogenated butyl rubber,ethylene-propylene-conjugated or non-conjugated diolefin terpolymers,polyisobutylene, styrene-butadiene rubbers, polybutadiene, polyisoprene,natural rubber and the various types of heretofore well known rubberscontaining either high or low olefinic unsaturation. Thecopolymerization of ethylene or propylene, with multiolefin such ashexadiene, dicyclopentadiene, norbornadiene, methylene norbornene,ethylidene norbornene, 1,5-cyclooctadiene, etc. are useful elastomers asstarting materials for sulfonation. Generally these polymers containbetween 0.2 and about 10.0 mole % unsaturation. As used herein, the term"olefinically unsaturated" is not intended to refer to aromatic typeunsaturation but to the aliphatic or cycloaliphatic type ofunsaturation. Butyl rubber and halobutyl rubber are well known articlesof commerce. In general, they have a viscosity average molecularweights, Mv, ranging between about 300,000 and 450,000. They areprepared conventionally as described in U.S. Pat. Nos. 2,356,128 and3,099,644. Lower molecular weight butyl rubbers may also be preparedhaving Mv of between about 30,000 and about 100,000. The methods ofproducing these low molecular weight butyl rubbers are described in U.S.Pat. No. 3,562,804. The corresponding chloro- or bromobutyl rubbers oflow molecular weight may also be prepared in conventional manner asdescribed in U.S. Pat. No. 3,104,235. For most purposes, the lowmolecular weight rubbers are not used alone but may be blended with thehigher molecular weight rubbers in order to give a calculated averagedviscosity average molecular weight intermediate between the high and lowmolecular weight rubbers, depending upon the properties desired in theadhesives to be produced and the specific uses for which they areintended.

The sulfonation, using either the SO₃ -complex described in theaforementioned U.S. Patent issued to Canter or the acyl sulfatesdescribed in Application Ser. No. 123,908, filed Mar. 12, 1971 and nowabandoned, is carried out so as to give a final sulfo rubber containingbetween about 0.1 and 5.0 mole % SO₃ H groups. The reactants, amounts ofreactants, and the reaction conditions are fully set forth in the Canterpatent and the pending application and are incorporated herein byreference.

Additionally, blends or admixtures of butyl rubber with natural rubber,of butyl rubber or chlorobutyl rubber with SBR, etc. may be employed asthe elastomeric components to be sulfonated. Similarly, in preparing thecombined cement hereinafter more fully described, previously, andseparately, sulfonated elastomers may be blended, after sulfonation,and, lastly, admixtures of sulfonated elastomers with unsulfonatedelastomers may be formed into blends and used in the hereinafterdescribed combined cements. As previously pointed out, mixtures, orblends of rubbers of differing molecular weight may be incorporated inorder to give a balanced intermediate viscosity average molecular weightto the final blend which is suitable for certain desired purposesbecause of the intermediate physical properties of the blend in contrastto that of the individual components of the blend.

The novel adhesive elastomeric contact cement compositions are prepared,using as the base of the cement composition, the heretofore describedsulfo derivatives of the olefinically unsaturated elastomers, in whichthe amount of sulfo groups ranges between about 0.1 and about 5.0 mole%, preferably between about 0.5 and about 2.0 mole %.

Additionally one of the more important components of the laminatedcement are the tackifiers. These are well known materials which haveheretofore been used to give tackiness and adhesion to variouselastomers. Not all types of tackifiers are suitable in the instantcomposition but all of the glassy organo thermoplastic resins havingsoftening or melting points above 50° C. have been found to besatisfactory in the instant novel cement composition. In general, theseare well known commercially available materials sold under varioustrademarks used as tackifiers in the rubber compounding industry, andare generally selected from the following specific classes:

alkyl phenol-formaldehyde resins

phenol-formaldehyde resins

petroleum hydrocarbon resins

chlorinated biphenyls

rosin-pentaerythritol resins

coumarone-indene resins

polyterpene resins, and

similar thermoplastic materials. These are employed in amounts rangingbetween about 5 and 90 parts phr (per hundred parts of rubber).Preferably they are employed in amounts ranging between about 30 andabout 60 parts phr.

Fillers of conventional type are also utilizable to give added body tothe ultimate laminate adhesives layer. These may be talcs, clays,calcium carbonates, carbon blacks, silicas, and the like. They aregenerally used optionally and, if used, are present in amounts rangingbetween about 5 and 50 parts phr.

The solvents employed are generally of the organic type or they are ofthe mixed solvent type in which at least one of the solvents is a polarsolvent. The strictly organic hydrocarbon type solvents may be benzene,toluene, tetrahydrofuran, or other similar types. On the other hand,mixed solvents generally give better cements because of their solvationcharacteristics. Such solvents may be branched chain alcohols, i.e. apolar solvent, or dioxane, coupled with cyclohexane, benzene or tolueneor coupled with tetrahydrofuran. These provide excellent cements havingstability on standing. Any other suitable solvents, customarily employedin forming elastomeric cements, which are, in fact, solvents for theconcentration of the sulfo elastomers incorporated, may also beemployed. For the most part, this selection of the organic solvent ormixed solvents forming the cement is a matter of choice and convenience.It should be understood, however, that the solvent, or mixed solvents,employed do, in fact, possess sufficient volatility characteristics sothat, once a laminate is formed, substantially all of the solvents areevaporated at ambient temperatures and pressures within a reasonablelength of time, i.e. a matter of 1-24 hours, since it is desired thatthe adhesive bonding layer be substantially devoid of solvent once thelaminate has reached a static condition. In general, the cements willcontain between about 10 and about 50 wt. % total solids, preferablybetween about 15 and about 25 wt. % total solids. A preferred solventconsists of 90 parts by weight of toluene admixed with 10 parts byweight of isopropyl alcohol.

Also the sulfonated elastomers employed may be incorporated into thecements in an unneutralized (acidic) form. Best results, however, havebeen attained where the sulfo groups have been at least partiallyneutralized, preferably, completely neutralized. The neutralizing agentsemployed may be any inorganic or organic base such as for example thealkali metal or alkaline earth metal hydroxides or carbonates, forexample, potassium hydroxide, sodium hydroxide, calcium hydroxide,sodium carbonate, potassium carbonate, calcium or barium carbonate, etc.The organic bases which are generally employed are the amines. These areeither the mono-, di- or triamines. They may be heterocyclic, alicyclic,or aliphatic, in nature, and they may contain polar groups as well.Specific examples of the amines that may be employed are methylamine,dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine,n-butylamine, di-n-butylamine, tri-n-butylamine and in fact any mono,di, or tri (C₁ -C₈ alkyl) amine. Examples of heterocyclic amines thatmay be employed are pyridine, piperazine, and pyrolidine. Examples ofamines containing polar groups which have been found to be satisfactoryare the alkylol amines such as mono-, di- or triethanol amine andnitrilo-tri-acetic acid. Other amines containing other polar groups suchas chlorine, carbonyl and ether groups may also be used in addition tothose containing hydroxyl and carboxyl groups. It is preferred toneutralize the sulfo groups with an amine of these types, preferably,ethylamine. Surprisingly, improved results are attained when all of thesulfo groups have been neutralized with an amine.

Various types of substrates to which the cements are adhered are eitherof the porous or non-porous type and they may be either organic orinorganic in nature. The surfaces to be adhered to one another by meansof the adhesive contact cement are merely sprayed, brushed, dipped orotherwise coated with the cement to a thickness of from about 1 to 15mils, after which they are contacted with one another under mildpressure for a sufficient length of time to allow the solvent of thecement to vaporize therefrom leaving the solid material in place as theintermediate layer of the laminate. The various types of materials usedas substrates are as follows:

Porous materials such as, textile fibers, cloth of cotton, wool, silk orsynthetic fibers such as polyesters, nylon, paper, wood, paperboard, andthe like and non-porous materials such as strips or sheetings ofpolystyrene, polyurethane, cellophane, polypropylene, polyethylene,polyester Mylar, cellulose acetate and sheet metals such as strips orsheets of aluminum, copper, steel, etc. In order to illustrate thegeneral character of the invention, the following are given as examplesbut it is not intended that the invention be limited thereto.

EXAMPLE 1

Two butyl cements in normal hexane (3 liters) each containing 14.2 wt. %solids (butyl rubber of Mv 350,000) were each reacted with 8.24 cc and16.48 cc, respectively of an acetyl sulfate solution. The acetyl sulfatesolution was made up by reacting 23.4 mls of acetic anhydride with 11mls of 96% sulfuric acid. The two cements were separately neutralizedwith stoichiometric amounts of ethylamine (70% in H₂ O) and 0.6 grams ofphenyl-beta-naphthylamine was added as an antioxidant. The polymers werethen steam stripped, and hot mill dried. Polymer #1 contained 0.7 mole %of SO₃ ⁻ EA⁺ (ethylamine) and polymer #2 contained 1.5 mole % of SO₃ ⁻EA⁺ (ethylamine).

EXAMPLE 2

Polymer #2 of Example 1, containing 1.5 mole % of ethylamine fullyneutralized SO₃ H groups, was dissolved at 20 wt. % total solids in a90-10 toluene-isopropyl alcohol solution. It had a Brookfield solutionviscosity of 7000 cps. A cast, dried film of this cement, 6 mills thick,exhibited a tensile strength of 3850 lbs. per square inch and anelongation at break of 1050%. This cement was used to laminate cottonduck cloth to cotton duck cloth, cotton duck cloth to steel, andpolypropylene film to polypropylene film. Adhesion of these substrateswas measured by an Instron Peel test measurement at a pull rate of 2inches/min. at 72° F. In the case of the cotton duck cloth laminated tocotton duck cloth, the T-peel adhesion measured on the Instron testerwas 25-30 psig. In the case of the cotton-duck cloth adhering to thesteel panel the 180° peel adhesion was 3 psig and in the case of thepolypropylene film laminated to polypropylene film, the T-peel adhesionwas 1 psig.

EXAMPLE 3

747 grams of butyl rubber of Mv 350,000 was dissolved in hexane to theextent of 16.7 wt. % solids and was placed in a 5 liter flask equippedwith a stirrer. 6.25 cc of acetyl sulfate, prepared as per Example 1,was added to the cement and reacted for 30 minutes at ambienttemperatures. 50 cc of isopropyl alcohol and 0.25 grams of anantioxidant, 2.6 di-tert-butyl-4-methylphenol were added. The cement wasused in this acid form for adhesion tests.

EXAMPLE 4

The sulfo butyl polymer cement described in Example 3 was applied tosubstrates, laminated, dried and tested on an Instron tester at roomtemperature. A laminate was prepared of cotton duck cloth to cotton duckcloth with an intermediate layer of the aforementioned cement in itsfree acid form. It had a T-peel adhesive strength of 15 psig whenpulled, as in Example 2, at 2 inches per minute on the Instron Tester.

The sulfobutyl polymer cement of Example #3 was fully neutralized withethylamine. This fully neutralized cement was used to laminate cottonduck cloth to cotton duck cloth, as described above. It had a T-peelstrength under the same conditions of 16 psig.

In contrast, a control sample of unsulfonated butyl rubber cement whenused to laminate cotton duck cloth and tested, in the same manner, gavea T-peel strength at only 6 psig.

The unneutralized sulfobutyl cement of Example 3 was used to laminatecotton duck cloth to sheets of steel. This laminate was dried and testedin an 180° peel test at 2 inches/min. on an Instron Tester at roomtemperature and yielded an adhesive strength of 3.5 psig. Thisunneutralized sulfobutyl polymer cement was then fully neutralized withethylamine. This fully neutralized cement was also used to laminatecotton duck cloth to sheets of steel, as described above. It had a 180°peel strength, under the same conditions of 0.2 psig. In contrast, acontrol sample of unsulfonated butyl rubber cement when used to laminatecotton duck cloth to sheets of steel and tested in the same manner gavea 180° peel strength of zero psig.

EXAMPLE 5

100 parts of sulfobutyl rubber of Mv 350,000 containing 1.5 mole % ofsulfonic acid groups, fully neutralized, partially neutralized, and inthe free acid form were admixed with 45 parts per hundred parts ofrubber of Wingtack 95 (a petroleum hydrocarbon resin with a softeningpoint of approximately 95° C.) and dissolved to the extent ofapproximately 25 wt. % solids in a mixture of 90 parts toluene and 10parts of isopropyl alcohol. Each of these three cements were applied tosubstrates in a thickness of approximately 5 mils. The substrates wereimmediately laminated and dried at 23° C. for 24 hours and then testedon an Instron tester at room temperature at a rate of 2 inches perminute.

                  TABLE I                                                         ______________________________________                                                     T-Peel        180° Peel                                                Cotton Duck-Cotton                                                                          Cotton Duck-Steel                                  Polymer      Duck lbs/in.  lbs./in.                                           ______________________________________                                        Sulfobutyl, 1.5 mol. %                                                                     24            3.0                                                fully neutralized with                                                        ethylamine                                                                    Sulfobutyl, 1.5 mol. %                                                                     23            1.5                                                .35/l partially neutral-                                                      ized with ethylamine                                                          Sulfobutyl, 1.5 mol. %                                                                     18            6.8                                                unneutralized                                                                 ______________________________________                                    

EXAMPLE 6

In order to demonstrate the highly desirable properties of retention ofstrength and adhesion under conditions of elevated temperatures, asulfobutyl rubber substantially identical with that produced in Examples1 and 3 but fully neutralized with sodium hydroxide instead ofethylamine was compared with an SBR Block copolymer (Kraton 1101) as agum polymer film. These films had the following tensile strengths underthe following temperature conditions.

                                      TABLE II                                    __________________________________________________________________________    Samples prepared from                                                         20 Mil thick molded                                                                        Sulfobutyl,                                                      pads, tested on an                                                                         2 Mole % SO.sub.3 Na,                                                                   SBR Block                                              Instron at 20/in/min.                                                                      Fully neutralized                                                                       Copolymer(Kraton 1101)                                 __________________________________________________________________________    Tested at 25° C.                                                       Tensile Strength, psi                                                                      3000      3900                                                   Elongation, %                                                                               800       550                                                   Tested at 50° C.                                                       Tensile Strength, psi                                                                      2200      2000                                                   Elongation, %                                                                               850      1500                                                   Tested at 75° C.                                                       Tensile Strength, psi                                                                      2000       400                                                   Elongation, %                                                                              1000      1150                                                   Tested at 100° C.                                                      Tensile Strength, psi                                                                      1800       80                                                    Elongation, %                                                                              1100       150                                                   __________________________________________________________________________

A similar sulfobutyl rubber having 1.5 actual mole % SO₃ H groups, butfully neutralized with ethylamine, in a cement of 90-10toluene-isopropyl alcohol to the extent of 20 wt. % total solids wasapplied separately to two cotton duck cloth substrates, laminated, driedat room temperature for a period of 24 hours and tested for its adhesionstrength on an Instron tester at 2 inches per minute under varyingtemperature conditions. The following T-Peel strengths were obtained, atthe temperatures indicated in Table III.

                  TABLE III                                                       ______________________________________                                        T-Peel, lbs/inch                                                              Cotton Duck - Cotton Duck                                                     Tested at 25° C.                                                                           25                                                        Tested at 35° C.                                                                           24                                                        Tested at 50° C.                                                                           26                                                        Tested at 100° C.                                                                          18                                                        ______________________________________                                    

EXAMPLE 7

Sulfobutyl rubber of 1.5 mole % SO₃ H, either fully neutralized withethylamine, or in the free acid condition, was dissolved in a 90/10mixture of toluene/isopropyl alcohol (IPA) (20 wt. % solids). Wingtack95 (a petroleum hydrocarbon resin with a softening point atapproximately 95° C.) or Amberol ST-137X (a phenol-formaldehyde resinwith a melting point of approximately 70° C.) was used as a tackifier inthe amount of 60 phr level in these cements. These cements at solidsthickness of about 5 mils were used as the adhesive layer to laminatelayers of cotton duck cloth to cotton duck cloth. The Cotton ducklaminates were tested in a T-peel adhesion test at the rate of 2 inchesper minute at various temperatures with the results shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        Cements applied to substrates, laminated, dried and                           tested as described. Adhesion pulled on an Instron                            at 2 in./min                                                                  Compounds            A       B       C                                        ______________________________________                                        Sulfobutyl, 1.5 mol %, SO.sub.3 EA fully                                                           100     100     --                                       neutralized                                                                   Sulfobutyl, 1.5 mol %, SO.sub.3 H                                                                  --      --      100                                      unneutralized                                                                 Wingtack 95 resin    60      --      --                                       Amberol ST-137 X resin                                                                             --      60      60                                       Solvent, Toluene/IPA, 90/10                                                   T-Peel, lbs/in.                                                               Cotton Duck-Cotton Duck                                                       Pulled at 22° C.                                                                            28      16      21                                       Pulled at 60° C.                                                                            26      13      12                                       Pulled at 80° C.                                                                            16      9       10                                       Pulled at 105° C.                                                                           11      2.5     --                                       ______________________________________                                    

The data appearing in Tables II, III and IV amply demonstrate thatsulfobutyl adhesive systems show good adhesive retention properties evenat temperatures as high as 100° C. although their highest adhesionretention properties hold only up to temperatures about as high as 50°C.

EXAMPLE 8

Compositions A & B of Example 7, Table IV, were used to laminate cottonduck to steel panels. The laminates were dried at room temperature for24 hours and then immersed in water for 24 hours at 90° C. This run wascarried out in order to test the effect of water immersion at elevatedtemperature. The samples were removed from the water, conditioned atroom temperature for 4 hours, and tested. The Instron test for 180° peeladhesion was carried out at 2 inches per minute. The following resultswere obtained.

                  TABLE V                                                         ______________________________________                                        Compound             A         B                                              ______________________________________                                        Sulfobutyl 1.5 mol %, fully                                                   neut.                100       100                                            Wingtack 95 Resin    60        --                                             Amberol ST-137X Resin                                                                              --        60                                             Solvent, Toluene/IPA, 90/10                                                   180° Peel, lbs./in.                                                    Cotton Duck to Steel                                                          Pulled at 22° C. (no water                                             immersion)            5         8                                             Pulled at 22° C. (after                                                water immersion - 24 14        23                                             hours at 90° C.)                                                       ______________________________________                                    

It can be seen from these data (Table V) that water immersion for 24hours at 90° C. results in a greatly increased adhesion between thesubstrates.

Similarly, a conventional bake cycle greatly improves the adhesionproperties of these cements when used to laminate cotton duck, (a porousmaterial) to steel plates (a non-porous material). Table VI shows thesame cements as adhesive layers (thickness of about 5 mils) betweencotton duck cloth and steel sheeting. The Instron 180° peel adhesiontest was conducted at room temperature at the rate of 2 inches perminute after the laminates had been subjected to a series of oven bakecycles at different times and temperatures.

As can be seen, the sulfobutyl cements of compositions A and B (TableVI) show a greatly improved adhesive strength after undergoing a bakecycle. When baked at a temperature of 150° C. for 1 hour, such a strongadhesion between the cotton duck cloth and the steel panel developedthat failure was by reason of cotton duck cloth rupture and not at theadhesive layer interface between the steel panel and the cotton duckcloth. Comparative Example C (Table VI) shows that an ordinary highmolecular weight butyl rubber cement shows some improved adhesion aftera bake cycle but is still at a level substantially below that for thesulfobutyl cements.

                  TABLE VI                                                        ______________________________________                                        Cements applied to substrates, laminated, dried and then subjected            to a bake cycle, as indicated, in a circulating air oven.                     Adhesion tested on an Instron at 2 in./min. at room temperature.              Compound          A        B        C                                         ______________________________________                                        Sulfobutyl, 1.5 mol.% SO.sub.3 EA                                                               100      100      --                                        Fully neutralized                                                             Butyl Rubber      --       --       100                                       Wingtack 95 Resin 60       --       60                                        Amberol ST-137X Resin                                                                           --       60       --                                        Solvent, Toluene/IPA, 90/10                                                                     Yes      Yes      --                                        Solvent, Toluene, 100                                                                           --       --       Yes                                       180° Peel, lbs./in.                                                    Cotton Duck to Steel                                                          No bake cycle      5        9        2                                        After Bake Cycle of -                                                         0.5 Hrs, at 70° C.                                                                        7       --       --                                        1 Hr. at 70° C.                                                                          12       --       --                                        3 Hrs. at 70° C.                                                                         17       --        6                                        24 Hrs. at 70° C.                                                                        38       22       13                                        3 Hrs. at 100° C.                                                                        26       22       --                                        5 Min. at 120° C.                                                                         8       --       --                                        15 Min. at 120° C.                                                                       15       --        6                                        1 Hr. at 120° C.                                                                         26       23       10                                        1 Hr. at 150° C.                                                                         29       30       --                                        ______________________________________                                    

The T-peel test is carried out as described by the method designated inASTM D-1876-69.

The 180° peel test is carried out as described by the method designatedASTM D-903-49 (reapproved 1965).

EXAMPLE 9

A butyl rubber cement 2108 grams (17.2 wt. % butyl rubber of Mv 350,000in n-hexane) was placed in a 5 liter flask equipped with a stirrer andcondenser. Acetyl sulfate in the amount of 15.2 cc was added and thereaction allowed to proceed for 30 minutes. The acetyl sulfate wasprepared as shown in Example 1. Thereafter 45 grams of triethanol aminewere added to fully neutralize the sulfobutyl reaction product (1.3 mole% SO₃ H groups) and the normal hexane was replaced with a like amount ofa solution mixture of 90 parts toluene, and 10 parts isopropyl alcohol.

EXAMPLE 10

The same procedure was followed as in Example 9 except that thesulfonated butyl rubber cement (2737 grams) was prepared using 26.7 ccof acetyl sulfate to give a mole % sulfo groups incorporated in thebutyl polymer in the amount of 1.6 mol % SO₃ H. This material was fullyneutralized with 34.6 grams of ethylamine.

EXAMPLE 11

The same procedure was followed as in Example 9 except that 9.75 cc ofacetyl sulfate was employed to give a 0.9 mole % of sulfo groups in thesulfonated butyl rubber cement (2001 grams) and this was fullyneutralized with 97.5 cc of 2N NaOH.

EXAMPLE 12

The neutralized polymer cement of Examples 9, 10 and 11 were eachformulated with 45 phr of Schenectady SP-134 (an oil soluble, heatreactive, phenolic resin with a melting point of approximately 70° C.)and tested as adhesive bonding films. Aluminum to aluminum laminateswere formed by placing the bonding film between plates of aluminum underabout 150 psi pressure and a temperature of 125° C. for 30 minutes. Thetest specimens had a total bonded contact area of 2 square inches. Thesamples were then pulled on an Instron tester at a rate of 2 in./min.until rupture (Table VII). The force in pounds per square inch atrupture was measured.

The low temperature flexibility of these adhesive bonding films was alsotested. The aluminum to aluminum laminate (as above described) wereplaced in a cold box (-15° C.) for 2 hours and tested in thisenvironment by attempting to rupture the bond by hand flexing. Thesamples did not fail. (Table VII).

These data clearly demonstrate the good strength and good lowtemperature properties of adhesive bonding film formulated usingsulfobutyl elastomers. More particularly, sulfobutyl rubber neutralizedwith a functional amine, i.e. triethanolamine, exhibits especiallysuperior adhesive properties.

                  TABLE VII                                                       ______________________________________                                                          Example  Example  Example                                   Polymers of       9        10       11                                        ______________________________________                                        Schenectady SP 134 (phr)                                                                         45       45       45                                       Shear Strength psi                                                            at 23° C., 2 in/min. on                                                an Instron tester  450      350      200                                      Bond Strength at low                                                          temperature (-15° C.)                                                  Hand Flex         -- Did not Fail --                                          Brittle Point ° C.                                                                       -60      -60      -60                                       ______________________________________                                    

In general, the better adhesion of the sulfo elastomer to metal such assteel or aluminum was attained if the free acid or unneutralized form ofthe sulfo elastomer was used but for other substrates the partially andfully neutralized forms of the sulfo rubbers appeared to give higheradhesion strengths. To some extent, however, improved adhesion strengthswere obtained using partially neutralized or fully neutralized sulforubbers adhered to smooth metal surfaces where after application of thesulfo rubber cement to the metal surface and the lamination thereof, thecomposite laminate was subjected to elevated temperatures of from about70° C. for 24 hours to about 150° C. for 1 hour.

Having now thus fully described and illustrated the character and natureof this invention, what is desired to be secured by Letters Patent,

What is claimed is:
 1. A liquid adhesive elastomeric contact cement composition consisting of a sulfo derivative of an olefinically unsaturated butyl rubber having a viscosity average molecular weight of about 100,000 to about 450,000 containing between about 0.1 and about 5.0 mole percent of sulfo groups, and, as a tackifier, between about 5 and about 90 parts by weight of at least one organo thermoplastic resin having a softening or melting point of above 50° C., per hundred parts by weight of butyl rubber, dissolved in an organic solvent or mixture of organic solvents, said cement composition containing about 10 to about 50 weight % solids, said solvent or solvents being sufficiently volatile to substantially all evaporate at ambient temperatures and pressures.
 2. A cement composition as in claim 1 wherein the solvent is a mixture of solvents at least one of which is a polar solvent.
 3. A cement composition as in claim 2 wherein the sulfobutyl rubber has an Mv of between about 300,000 and about 450,000 and the solvent is a mixture of solvents at least one of which is a polar solvent.
 4. A cement composition as in claim 1 wherein the sulfo butyl rubber is at least partially neutralized with an organic amine or an inorganic base.
 5. A cement composition as in claim 4 wherein the tackifier is a phenol formaldehyde resin.
 6. A cement composition as in claim 4 wherein the tackifier is a petroleum hydrocarbon resin and the solvent is a mixture of toluene and isopropyl alcohol.
 7. A cement composition as in claim 5 wherein the butyl rubber contains between about 0.05 and about 2.0 mol % sulfo groups, is fully neutralized with ethyl amine, and contains about 60 parts phr of a phenol formaldehyde resin tackifier. 